<?php

/** 
* @version 1.0 
* @author   bolted snail 
* @date 2011-10-15 
* @email 672308444@163.com 
* @PHP验证码类 
* 使用方法： 
* $image=new Captcha(); 
* $image->config('宽度','高度','字符个数','验证码session索引'); 
* $image->create();//这样就会向浏览器输出一张图片 
* 如： 
* new Captcha(80,20,4,'captcha_code'); 
* //所有参数都可以省略， 
* 默认是：宽80 高20 字符数4 验证码session索引captcha_code 
* 第四个参数即把验证码存到$_SESSION['captcha_code'] 
* 最简单使用示例: 
* $image=new Captcha(); 
* $image->create();//这样就会向浏览器输出一张图片 
*/  




class Captcha {

  private $width=80,$height=20,$codenum=4;  
  public $checkcode;     //产生的验证码  
  private $checkimage;    //验证码图片   
  private $disturbColor = ''; //干扰像素  
  private $session_flag='captcha_code';//存到session中的索引  
    
  //尝试开始session  
  function __construct(){  
      @session_start();  
  }  
  /* 
  * 参数：（宽度，高度，字符个数） 
  */  
  function config($width='80',$height='20',$codenum='4',$session_flag='captcha_code')  
  {    
     $this->width=$width;  
     $this->height=$height;  
     $this->codenum=$codenum;  
     $this->session_flag=$session_flag;  
  }  
  function create()  
  {  
     //输出头  
     $this->outFileHeader();  
     //产生验证码  
     $this->createCode();  
    
     //产生图片  
     $this->createImage();  
     //设置干扰像素  
     $this->setDisturbColor();  
     //往图片上写验证码  
     $this->writeCheckCodeToImage();  
     imagepng($this->checkimage);  
     imagedestroy($this->checkimage);  
     $_SESSION[$this->session_flag]=$this->checkcode;  
  }  
  /* 
     * @brief 输出头 
     */  
  private function outFileHeader()  
  {  
    header('Cache-Control: private, max-age=0, no-store, no-cache, must-revalidate');
    header('Cache-Control: post-check=0, pre-check=0', false);    
    header('Pragma: no-cache');
    header ("Content-type: image/jpeg");  
  }  
  /** 
     * 产生验证码 
     */  
  private function createCode()  
  {  
     $this->checkcode = strtoupper(substr(md5(rand()),0,$this->codenum));  
  }  
  /** 
     * 产生验证码图片 
     */  
  private function createImage()  
  {  
     $this->checkimage = @imagecreate($this->width,$this->height);  
     $back = imagecolorallocate($this->checkimage,255,255,255);   
     $border = imagecolorallocate($this->checkimage,0,0,0);    
     imagefilledrectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$back); // 白色底  
     imagerectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$border);   // 黑色边框  
  }  
  /** 
     * 设置图片的干扰像素  
     */  
  private function setDisturbColor()  
  {  
     for ($i=0;$i<=200;$i++)  
     {  
      $this->disturbColor = imagecolorallocate($this->checkimage, rand(0,255), rand(0,255), rand(0,255));  
      imagesetpixel($this->checkimage,rand(2,128),rand(2,38),$this->disturbColor);  
     }  
  }  
  /** 
     * 
     * 在验证码图片上逐个画上验证码 
     * 
     */  
  private function writeCheckCodeToImage()  
  {  
     for ($i=0;$i<$this->codenum;$i++)  
     {  
      $bg_color = imagecolorallocate ($this->checkimage, rand(0,255), rand(0,128), rand(0,255));  
      $x = floor($this->width/$this->codenum)*$i;  
      $y = rand(0,$this->height-15);  
      imagechar ($this->checkimage, rand(5,8), $x+5, $y, $this->checkcode[$i], $bg_color);  
     }  
  }  
  function __destruct()  
  {  
     unset($this->width,$this->height,$this->codenum,$this->session_flag);  
  }  
}  

?>








